1. Field of the Invention
Apparatuses and methods consistent with the present invention relates to digital rights management, and more particularly, to digital rights management, whereby a licensing work centering around a rights object issuer can be performed in respective devices.
2. Description of the Prior Art
Recently, digital rights management (DRM) has been researched actively, and commercial services using this DRM have already been used or will be used. A technical concept of DRM is to protect digital content of which illegal copying and distribution can be easily performed.
Some efforts have been made to protect the digital content. In the related art, digital content protection has been concentrated on preventing an access to digital content without permission. For example, only those people who have paid charges are permitted to access the digital content. However, a person who has not paid the charges cannot access the digital content.
However, due to the characteristics of digital data, digital content can be readily copied without loss, reused, processed and distributed to third parties. Accordingly, when a person who has paid the charges accesses the digital content and intentionally distributes it to a third party, the third party can use the digital content without paying the charges, from which a number of problems have been caused.
In order to solve these problems, in DRM, digital content is encrypted and distributed, and in order to use the encrypted digital content, a license that is called a rights object (RO) is required.
FIG. 1 is a view illustrating a related art system for digital rights management. Referring to FIG. 1, a device 10 can obtains digital content from a content provider 20. In this case, the digital content provided by the content provider 20 is in an encrypted state, and in order to use the encrypted digital content, a rights object is required.
The device 10 can obtain the rights object including rights to use the encrypted digital content from a rights object issuer 30, and for this a user should pay a predetermined charge.
The rights object includes a key for decrypting the encrypted digital content.
The rights object issuer 30 reports details of rights object issuance to the content provider 20, and according to circumstances, the rights object issuer 30 and the content provide 20 may be the same subject.
The device 10 having acquired the rights object can use the encrypted digital content by consuming the rights object.
On the other hand, encrypted digital content may be freely copied and distributed to other devices (not illustrated). However, since the rights object includes information about the limitation of the number of times for which the encrypted digital content can be used, a duration, the number of times for which the copy of the rights object is permitted, and so forth, it should be limited by reuse or copy. According to this DRM technology, digital content can be effectively protected.
However, in the related art DRM system as illustrated in FIG. 1, in order for the device 10 to share content with another device (not illustrated), the other device should receive the rights object from the rights object issuer 30 through a separate process.
In other words, the sharing of content between devices is not free, and the device having received the encrypted digital content should communicate with the rights object issuer 30 to obtain the rights object. This is because the change of the rights object such as an update, correction, and transfer of the rights object, i.e., a licensing work, is performed by the rights object issuer 30.
In addition, if a second device that does not belong to a domain of a first device intends to share the encrypted digital content that can be shared in the domain with the first device, in a state that the first device shares a key and belongs to the domain as a logical set in which the content sharing is possible, the second device should pass through a separate process for subscribing the domain to cause inconvenience in use.
In this respect, there is a growing need to share encrypted digital content between devices in a more convenient method.